Bedridden patients who have to maintain a substantially motionless position for prolonged periods of time develop bedsores on the skin. These sores, referred to in medical terms as Decubitus Ulcers, are painful, hard to heal, and create conditions for further infection. Ulcer formations of this type are produced in most cases because the pressure exerted upon the skin surfaces under the bony prominences of the patient which bear most of the weight of the patient when the body of the patient presses against the ordinary mattress or other body support and obstructs the circulation of blood in the capillaries directly under these surfaces.
It is known that large, very deep water filled containers (waterbeds) of large size and weight permit the patient to float freely in such a manner that the pressure exerted upon the weight bearing surface of the patient's body is distributed uniformly, eliminating regions of high pressure under the bony prominences whereby the ulcers do not form. These large waterbeds are covered with a top plastic sheet free of tension. The patient, placed upon this sheet, does not get wet but effectively floats deep in water. However, waterbeds of such depth are much too large and too costly for general use.
When the depth and the size of the waterbed are both reduced to more convenient and smaller dimensions, as is done with the light weight water flotation mattresses, the upper surface of the mattress upon which the body is placed is subjected to a tension or stretch force which produces undue pressure against the skin, in particular under the bony prominences. The patient does not float in the same manner as in a waterbed because the body is supported by a combination small buoyancy force and more dominant stretch force in the upper plastic sheet that is supporting the body. In the ideal situation using a water bed, the downwardly directed weight of the patient's body at any point along the body is counterbalanced by a force directed vertically upward by the buoyancy forces of water alone. The plastic sheet in such a case under the body of the patient and above the water is free to adjust to the contour of the patient causing no pressure whatsoever. Such an arrangement provides the best conditions for prevention of bedsores. However, when the sheet is not free to adjust, as in the case of a small light weight water mattress, the skin area supporting body weight is reduced, the depth of flotation is decreased, and most of the counterbalancing, body supporting force is derived from the stretch in the top sheet of the mattress caused by the height of the water. As the surface is depressed in accordance with the body contour and weight of the patient, unequal forces are transmitted via the surface stretch tension of the mattress. As a result regions of high pressure are created, mainly under the bony prominences, compressing the underlying capillaries, causing obstruction of blood circulation as previously described.
Another type of small size mattress has been developed to deal with the problems of bedsores formation. This type of mattress is adapted to be filled with air. The whole surface of the mattress is divided in small parallel chambers, or regions, tied together in two side by side groups. When one of the groups is inflated, the other adjacent group is deflated, providing at all times an area for the body that is not resting on the mattress, but is almost completely relieved from pressure. The adjacent groups of cells are alternatively inflated and deflated producing a massaging action.
Such air mattresses are not as effective as water filled mattresses in inhibiting ulcer formation.
This inferior performance is inherent in the geometry because the air pressure in the inflated region is more than twice as high as it would be if the entire mattress were to be completely inflated because more than half of the skin area is excluded from participating in supporting the total body weight. The massaging action ameliorates but does not fully eliminate the adverse effects of localized high pressures.
In copending application Ser. No. 295,504, filed 4/24/81, now U.S. Pat. No. 4,422,194 there is disclosed a new type of body support that can be used with water or air. This support employs a first plastic section having oppositely disposed inner and outer surfaces. The outer surface is disposed above the inner surface and permanently defines a plurality of closely spaced raised regions of like size and contour which are interconnected by channels disposed below the walls of the regions. The inner surface of the first section permanently defines a like plurality of deep recesses, each deep recess constituting the inside of a corresponding region. The deep recesses are interconnected by shallow recesses, each shallow recess constituting the inside of a corresponding channel.
A second plastic section is sealed to the inner surface of the first section in a manner in which said deep and shallow recesses communicate with each other. A flexible hollow tube is disposed around the periphery of said sections and is secured thereto. The tube has an outer wall with openings which connect the tube interior to said shallow recesses. The tube and sections are sealed to each other in a leak-proof manner to prevent leakage of air or water between the interior of the tube and sections and the outside thereof.
This combination of tubes and sections thus has a hollow interior with deep and shallow recesses and tube interior being interconnected. In use, the interior is completely filled with water or air.
When a patient sits upon the device, as, for example, when the patient is on a wheel chair, or when the patient lies upon the device of larger size when it is used as a mattress, the various raised regions conform independently without stretch tension to the body contour and, because of the intercommunicating hollow regions, the shallow channels and tube distribute the water or air as required. As the patient shifts in bodily position, the water or air movement adjusts the shape of the device accordingly.
The raised regions are depresed when conforming to the body contour and spread sideways to close the gaps therebetween, thus providing a continuous support between the spread regions and the body of the patient. Unlike the prior art devices, the top portions of the raised regions are not subjected to appreciable stretch-tension forces since the tube substantially eliminates sideways deformation of the raised regions which would otherwise produce such forces with the resultant adverse effects previously described. The use of the tube filled with water or air permits the raised regions that are not underneath the body to remain upright whereby the surface stretch in the rest of the raised regions under the body stretch-tension is minimized, and the pressure on the skin is also minimized, thus minimizing ulcer formation.
The present invention is based upon the discovery that the tube and section structure described in the aforementioned copending application can be made even more effective in reducing ulcer formation when the central sections are water filled and at the same time the peripheral tube is filled with air. Moreover, this combined use of an air filled tube and water filled sections enables a new type of mattress which is relatively inexpensive to manufacture and which, as compared to other water filled mattresses, is considerably more effective and is easier to install or remove.